Summary

When humans invented farming 10,000 years ago, they weren't the only ones to get a boost from the new starchy diet. Some microbes that had lurked at low levels in the mouths of hunter-gatherers bloomed on the sugary films coating the teeth of farmers who munched cereal grains. Eventually the cavity-causing Streptococcus mutans, for one, took root. It adapted to the sweet life, multiplying like a weed and edging out many other species of bacteria. That leaves the modern mouth a depauperate ecosystem, according to two new genetic studies.